In testing and research carded out in chemical and biological laboratories and in the field, it is routine that substances will require mixing, or that agitation of some form or another will be necessary to promote a reaction or development time for a synthesis or a culturing or testing procedure. A variety of devices exist to carry out such agitation for extended periods of time. To be distinguished from devices such as magnetic and mechanical stirrers, which perform an agitating action directly on the substance or substances to be mixed or shaken, are shaking machines that employ a moving platform or shelf upon which is placed a plurality of vessels such as beakers and Erlenmeyer flasks. Movement of the shelf by an attached drive mechanism causes a corresponding agitation of the vessels and of any contents held therein. Such movement, depending on the drive mechanism of the shaking machine, is generally of a reciprocating or gyrating nature. While for some applications the type of agitation may be of little or no importance, for others, a completely successful result may only be achievable with an agitation motion that is of a certain type, that is, agitation by either a reciprocal or gyratal action, and/or agitation of a gentle or strong nature.
It is equally routine that, during such agitation, it will be required that a controlled temperature environment be maintained. In the case of shaking machines, such temperature control is usually carried out by immersing the substance-containing vessels, or a testing component, in a bath, the bath being supported by, or an integral part of, the moving shelf. The bath is typically a liquid bath of water; less frequently it is one of an oil or an organic solvent. A heating or cooling element connected to a temperature controller is generally used to maintain the desired temperature, the element either being immersed in the bath or in close external proximity thereto. Many applications, especially those relating to modern molecular biology and biochemistry, require an especially narrow temperature window, only within the limits of which is it possible to obtain satisfactory results.
Most of the bath shaking machines as are presently available are either noisy in operation, or are incapable of a gentle agitation motion, or both. They frequently do not allow for a narrow temperature control. Many bath shakers are bulky and heavy as well. U.S. Pat. No. 5,052,812, issued to Tannenbaum, et al., on Oct. 1, 1991, notes some of these problems while citing a comprehensive listing of relevant patents and commercial sources of conventional bath shakers. Typically, reciprocating bath shakers employ a rail or guide system that is inherently noisy due to travel by a sliding or rolling component along the rail or guide. Rail mechanisms, if precise and quiet, also tend to be very expensive, due to tolerance requirements. And gyrating bath shakers, whether noisy or otherwise, do not produce a motion that is desirable for many types of sensitive analysis and testing procedures. Because of the limitations associated with most presently available bath shakers, a substantial need still exists for a bath shaker that is quiet in operation, that takes up a minimal amount of space, and that is capable of producing an agitation motion and control of temperature environment that is compatible with modem testing procedures.